JOURNAL IMPACT FACTOR
3-year calculation window (2014, 2015, and 2016)
Document posted April 2017 2 DISCLAIMER
• The information herein applies to the Journal Impact Factor calculation for 2016, as published in the 2017 Journal Citation Reports (JCR).
• Clarivate Analytics, formerly the IP & Science business of Thomson Reuters, revisits the requirements for the Impact Factor calculation annually.
• Publishers can contact the Clarivate Publisher Relations team with questions: [email protected] 3 DEFINITION: JOURNAL IMPACT FACTOR
• Impact Factor is a journal-level metric; it is the average number of times a journal’s articles – specifically, those published in a 2-year period – were cited in 2016.
• Impact Factors are calculated for journals selected for and indexed in the Science Citation Index Expanded (SCIE) or the Social Sciences Citation Index (SSCI).
• Impact Factors are published annually in the Journal Citation Reports (JCR) 4 IMPACT FACTOR CALCULATION
• The Impact Factor is calculated by dividing the number of citations in the JCR year (the numerator) by the total number of citable items published in the 2 previous years (the denominator).
• An Impact Factor of 1.0 means that, on average, articles published 1 or 2 years ago were cited one time in 2016.
The Number of Citations Made to the Journal in 2016 to Content Published NUMERATOR in the Previous 2 Years (2014, 2015)
The Number of Citable Items Published DENOMINATOR During the Previous 2 Years (2014, 2015) 5 2017 JCR (2016 IMPACT FACTOR)
2013 2014 2015 2016 2017 All Previous Years
2016 Impact Factor Citations published in June 2017 JCR Source paper – published in 2016
Cited reference – published in 2014 or 2015
2016 citations to 2014 and 2015 content 2016 Impact Factor = Total # citable items published in 2014 and 2015 6 WHAT’S IN THE NUMERATOR?
• Citations are drawn from these • The following are not in indexes in Web of Science: the numerator: • Science Citation Index – Citations to articles, Expanded (SCIE) books, book chapters, • Social Sciences Citation Index or similar items (SSCI) indexed in other • Arts & Humanities Citation Web of Science Index (AHCI) datasets. • Emerging Sources Citation Index (ESCI) • The Science edition of the Conference Proceedings Citation Index (CPCI) • The Social Science and Humanities edition of the CPCI
7 WHAT’S IN THE DENOMINATOR?
COUNTED: NOT COUNTED: • Citable Items • Editorials – Original research • Discussions articles • Meeting abstracts – Review articles • Book reviews – Proceedings papers • News items – Technical notes • Letters or Commentaries, – Supplements: full unless they function as articles will count “articles,” such as the letters in Nature.
8 WHAT IS A “CITABLE ITEM”?
• Characteristics of a citable item include: – Usually an article, proceeding, or review, but not limited to these categories – Descriptive article title – Named author with address and funding information – Abstract – Article length – Cited references – Data content
9 TITLE CHANGES AND IMPACT FACTOR
How do title changes affect Impact Factor?
Year 1 • The new title is listed with an immediacy index: citations in the JCR year (2016) to content published in the JCR year (2016). • The old title is listed with normal Impact Factor.
Year 2 • The JCR lists separate Impact Factors for the new and the old titles.
Year 3 • The old title is no longer listed. • The new title appears with a normal Impact Factor. 10 SUPPLEMENTS AND IMPACT FACTOR
How are supplements and special issues handled?
• Citable items from these publications are counted in the denominator.
• Ensure that Clarivate is aware of these titles, especially if they fall outside the stated frequency of the journal. 11 TABLE OF CONTENTS AND IMPACT FACTOR
• My journal added a new section over the past 2 years. Is this change captured in the JCR?
– Adding new sections or changing existing sections in a currently indexed journal can affect the Impact Factor.
– Alert Publisher Relations to such changes: [email protected] 12 TITLE VARIANTS AND IMPACT FACTOR
• Authors cite journals inconsistently. Is the JCR still capturing the citations?
– Yes. Title variants are unified by the JCR team.
– A citation must include the journal title/variant and year to be calculated for the Impact Factor.
– Publishers are encouraged to provide clear instructions to authors on how to cite the journal, especially for “online first” or “publish ahead of print” articles. JCR JOURNAL SUPPRESSION 14 JCR JOURNAL SUPPRESSION
• Increasingly rare but still enforced
• Action primarily taken in response to excessive self citation and citation stacking
• Suppression is not de-selection; journals can remain indexed in Web of Science 15 16 17 FURTHER READING
Hubbard SC, McVeigh ME. Casting a wide net: the Journal Impact Factor numerator. Learned Publishing. 2011;24(2):133-7. http://dx.doi.org/10.1087/20110208
McVeigh ME, Mann SJ. The Journal Impact Factor Denominator: Defining Citable (Counted) Items. JAMA. 2009;302(10):1107-9. http://jama.jamanetwork.com/article.aspx?articleid=184527
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